Electronic organ system utilizing band elimination filters for minimizing beat effects



v Illa I l1 l l l I n l l I I n I l 1|J. 8 AI W E 5. mv... O` @LNmH0u\ojmo N AW we.. ....a.. m m QJ? L 7J m own Q J. r N d m 1 w T m Nmmom. mm v Q@ Do 7J EE mm wt om@ Em R y D w Emm w@ E: om@ EN memo. mmm oEzmz .T.,,.......--4 m- B l n [IO n m k o QQN. QN M d DM mu. uw wu @m @nm m m.. ma 3 1- 1j 1- m m @www2 @www w n- @KSL HMT ..-m G onwmmm ooNN nm m 55mm ow u 0m om@ @DLV 7 T u.. m C r 1l1||||||a||| .wm www@ o EN MMU@mm www@ n @N29 www Szm Q P. d. J U M United States Patent 3,511,918ELECTRONIC ORGAN SYSTEM UTILIZING BAND ELIMINATION FILTERS FOR MINIMIZING BEAT EFFECTS Donald J. Leslie, Altadena, Calif. Leslie Research C0.,267 S. Fair Oaks Ave., Pasadena Calif. 91101) Filed Jan. 10, 1966, Ser.No. 532,485 Int. Cl. Gh 1/00, 1/06 ABSTRACT OF THE DISCLOSURE In orderto avoid a major source of beat effects in an electric organ or othermusical instrument having complex generators, the third harmonic issuppressed. Accordingly, the third harmonic of any note cannot beat withthe second harmonic of the note in fifth musical interval relationshipsince the third harmonic doesnt exist. Also, the fourth harmonic of anynote cannot beat with the third harmonic of a note in fourth musicalinterval relationship because the third harmonic doesnt exist.

BRIEF SUMMARY OF THE INVENTION This invention relates to electronicorgans or similar musical instruments that generate complex signalscorresponding to the fundamental and harmonic components of musicalnotes.

It has been well established that certain beat effects are present insuch musical instruments. Thus, as explained in my prior patent No.2,596,258, issued May 13, 1952, and entitled Electric Organ SpeakerSystem, whenever two generators corresponding to notes in fourth musicalinterval relationship with respect to each other are simultaneouslyoperated, the fourth and third harmonics of the respective generatorsare separated in frequency by only one or two cycles per second; andwhenever two generators corresponding to notes in fifth musical intervalrelationship with respect to each other are simultaneously operated, thethird and second harmonics of the respective generators are similarlyseparated in frequency by only one or two cycles per second. If a singleelectrical channel combines signals from such generators, then a newfrequency component will be heard that goes on and olf at the rate ofabout once every second or two, and an annoying -beat effect results.Since fourth and fifth musical interval chords are common, such beateffects often occur. The beat effect is magnified by addition of tremoloand vibrato, such as by rotary apparatus shown and described in my priorpatent No. Re. 23,323, issued Ian. 9, 1951, and entitled RotatableTremulant Sound Producer.

In certain organ systems, a set of generators spanning several octavesis derived from a set of twelve master oscillators. In such systems, thesecond, fourth and eighth harmonics of any generator are precisely tunedto the generators for octaves above and below since generators in octaverelationship all derive from a common oscillator. However, the sixthharmonic of a generator has a frequency component that may beat withoctave harmonics of a generator in fifth musical interval relationship.

In order to avoid such annoying beat effects, I have heretofore proposedvarious systems. For example, in said Pat. No. 2,596,258, twoelectrical-acoustic channels are provided for generators in alternatehalf-tone relationship whereby electrical mixing of signals ofgenerators in fourth or iifth musical interval relationship isprecluded. In my prior patents No. 3,041,910, issued July 3, 1962,entitled Electrical Circuit Arrangement for Complex Wave Generators, No.3,049,040, issued Aug. 14, 1962, entitled Apparatus for Minimizing BeatEffects, and No.

3,080,786, issued Mar. 12, 1963, entitled Speaker System for AddingTremolo, multichannel systems are illustrated for solving this problem.While these systems are quite satisfactory, the addition of an extraelectrical-acoustic output channel s costly. Accordingly, the primaryobject of this invention is to provide a system for minimizing lbeateffects that requires but a single electric-acoustic channel.

The third harmonic component appears to be the major source ofdiiiiculty since it may beat with the second harmonic of anothergenerator as well as the fourth harmonic of still another generator.Accordingly, if the third harmonics of all generators can be suppressed,the beat problem will be avoided even though the second and fourthharmonics of the generators remain. I have discovered that the thirdharmonic can be eliminated Without significant `loss of characteristicvoicing of an organ. Thus only clarinet-type tone requires a strongthird. Other tones are not seriously affected by the absence of thethird harmonic. Accordingly, an excellent compromise is reached simplyby suppressing the third harmonic. The sixth harmonic is never dominantin any tone; hence, its suppression goes without significant notice.

Another object of this invention is to provide a set of complexgenerators each having a harmonic structure characterized by the absenceof the third and sixth harmonics.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of severalembodiments of the invention. For this purpose, there are shown a fewforms in the drawings accompanying and forming part of the presentspecification. These forms will now be described in detail, illustratingthe general principles of the invention; but it is to be understood thatthis detailed description is not to be taken in a limiting sense, sincethe scope of the invention is best defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a chart illustrating thefrequencies of harmonic components of generators for notes in fifthmusical interval relationship;

FIG. 2 is a chart illustrating the frequencies of harmonic components ofgenerators for notes in fourth musical interval relationship; and

FIG. 3 is a schematic diagram of an organ system incorporating thepresent invention.

DETAILED DESCRIPTION As shown in FIG. 1, the third harmonic of A (440)has a frequency that falls quite close to the frequency of the secondharmonic of E (659.26). If generators corresponding to A (440) and E(659.26) are simultaneously operated and mixed in the sameelectricalacoustic channel, the listener will perceive a frequencycomponent of about 1320 c.p.s. but which goes on and off or at leastincreases and decreases in amplitude at the rate of about one and a halfcycles per second. Thus the frequency components 1320 c.p.s. and 1318.52c.p.s. move into and out of reinforcing and bucking relationship at arate corresponding to the frequency difference.

In FIG. 2, the fourth harmonic of A (440) has a frequency that fallsquite close to the third harmonic of D (587.33). Accordingly, whengenerators for these notes are `simultaneously operated and translatedin the same electrical-acoustic channel, the listener will perceive afrequency component of about 1760 c.p.s., the amplitude of whichincreases and decreases at a rate of about two cycles per second,corresponding to the difference in frequency between 1760 c.p.s. and1761.99 c.p.s.

The charts shown in FIGS. l and 2 are typical, and it can similarly beshown that the third harmonic of a generator for any note produces likebeat problems with the second and fourth harmonics of other generators.Accordingly, by suppressing the third harmonic for all of thegenerators, the source of such beat effects will be eliminated.

In FIG. 3, there is illustrated a set of generators 8.

Each generator of this set produces signals rich in all harmonics. Atransducer for converting 'the electrical impulses into another form inthe present instance is a speaker system 10. The speaker system is shownin this instance as driven by several electrical output channels 12, 14,16, etc. Each of these electrical channels 12, 14 and 16 is controlledby a stop switch 18, 20 and 22 labeled, for example, Tibia, Oboe, Cello,etc. The number of electrical output channels is irnmaterial, butseveral are shown for illustrative purposes.

An electrical signal having a pitch C1 and a timbre corresponding totibia is applied to the Tibia channel 12 by operation of a key 24.Associated with the key 24 are a series of key switches 26, 28, 30, etc.for the electrical output channels 12, 114, 16, etc. Thus when the keyswitch 26 is closed, a circuit is established from the generator C1 asfollows: a lead 32, a band elimination lter 34 of conventional design,an isolation resistor 36, key

f switch 26, a lead 38, a shaping circuit 40 designed to impart suitabletibia characteristic to the signal, the stop vswitch 18, and theelectrical output channel 12.

Similarly, the switch 24, when closed, transmits to the Oboe channel 14a signal corresponding to the generator C1 but shaped to produce acharacteristic Oboe tone. Thus a circuit from the generator C, may betraced through the lead 32, the band elimination filter 34, an isolationresistor 42, the key switch 28, a lead 44, a shaping circuit 46, and thestop switch 20 to the electrical output channel 14.

The key switch 30 operates in a similar manner in connection with theCello output channel 16. Of course, a single key switch could serve inplace of the switches 2'6, 28 and 30` which transmit a common pitch.Other switches of the set could be used for coupling purposes.

Similar circuits are provided for the other generators of t-he set `8.Thus, associated with the electrical output lead 48 of the generator D#1is a band elimination filter 50 that connects to one side of keyswitches 52, 54 and 56 operated by a key 58. Serially associated withthe switches 52, 54 and 56 are Tibia, Oboe and Cello shaping circuits60, 62 and 164 that are interposed in leads `66, |68 and 70 to theelectrical output channels 12, 14 and 16. In a well-understood mannerthe keying system for the organ is thus provided, only a few of theconnections being shown by way of illustration.

Each generator, however, is provided with a band elimination filter,such as filter 34 or 50, that substantially attentuates the thirdharmonic. Thus the band elimination filter 34 for the generator C1 istuned to the frequency corresponding to the third harmonic of C1, andthe band elimination filter 50 for the generator `Dil is tuned to afrequency corresponding to the third harmonic of D1. The third harmonicsof all of the gnerators accordingly are suppressed, and no beat effectsoccur due to the interaction of the third harmonics either with thelsecond or fourth harmonics of other notes. Of course, the second andfourth harmonic components of the generators are passed by the bandelimination filters, the tuning of the filter being sufficiently sharpfor this purpose.

Individual generators of the set 8 together with their filters 34 may asa unit be considered a generator circuit that produces complex signalscontaining the second, fourth and other harmonics of the note, butsubstantially devoid of the third harmonic.

If desired, the suppression devices 34, 50, etc. could be split intocomponents and associated serially with the outputs of the shapingcircuits 40, 46, etc. Optionally the shaping circuits could be locatedbetween the key switches and the generators.

Illustrated in dotted lines in FIG. 3 are band elimination filters 72,74, 76, 78, etc., which are designed to suppress the sixth harmoniccomponents. Accordingly, these harmonic components cannot interfere withthe other harmonic components of companion generators of the set.

The inventor claims:

1. In an electrical instrument: a set of generators for producingcomplex signals rich in harmonics corresponding to notes in a musicalrange; an electrical-acoustic output channel; key switches foroperatively connecting the generators to the output channel; and a setof suppression circuits for the generators, each suppression circuitbeing interposed 'between the respective generators and theelectric-acoustic channel, each of said suppression circuits beingindividually tuned to suppress the third harmonic of the correspondinggenerator whereby beat effects with second and fourth harmonics of othergenerators are minimized; said -tuned suppression circuits imposing acharacteristic to the instrument that compromises its versatility.

2. The musical instrument as set forth in claim 1 together with a secondset of suppression circuits for the generators, each of said suppressioncircuits of the second ser being individually tuned to suppress thesixth harmonic of the corresponding generator whereby beat effects withoctave harmonics of other generators are minimized.

3. In an electrical musical instrument: a plurality of selectivelyoperable electrical output channels; common transducer means having aninput connected to all of Said channels; a set of generators forproducing complex signals rich in harmonics corresponding to notes in amusical range; key switch means for each of the generators; a set ofcircuits for the generators, each circui-t |being serially associatedwith the generators and said electrical outlput channels, and controlledby the respective key switch means, each of said circuits includingshaping means for imparting characteristic -tonal quality, and each ofsaid circuits also including individually tuned means for suppressingthe third harmonic of the corresponding generator; said tuned meansimposing a characteristic to the instrument that compromises itsversatility.

4. The musical instrument as Set fotrh in claim 3 in which a commonsuppressing means is provided for all of said circuits for eachgenerator.

S. The musical instrument as set forth in claim 3 in which each of saidcircuits also includes individually tuned means for suppressing thesixth harmonic of the corresponding generator.

6. In a musical instrument: an electric-acoustic output channel; a setof parallel input circuits for said channel, and corresponding to notesin a musical range; generator circuit means applying to said inputcircuits respectively, complex signals corresponding to the individualnotes, and containing the second, fourth and other harmonics of thenote, but substantially devoid of the third harmonic; means forindividually keying said generator circuit means; and a plurality ofselectively operable shaping circuit means separate from said generatorcircuit means and serially associated therewith for determiningcharacteristic voices of the instrument.

7. In a musical instrument: an electric-acoustic output channel; a setof parallel input circuits for said channel, and corresponding to notesin a musical range; generator circuit means applying to said inputcircuits respectively complex signals corresponding to the individualnotes and containing the second, fourth and other harmonics of the notebut substantially devoid of the third and sixth harmonic; means forindividually keying said generator circuit means; and a plurality ofselectively operable shaping circuit means separate from said generatorcircuit means and serially associated therewith for determiningcharacteristic voices of the instrument.

8. In an electrical musical instrument: a set of generators forproducing complex signals rich in harmonics corresponding to` notes in amusical range; an electricalacoustic output channel; key switches foroperatively connecting the generators to the output channel; and a setof suppression circuits for the genera-tors, each suppression circuitbeing interposed between the respective generators and theelectric-acoustic channel, each of said suppression circuits beingindividually fixed and narrowly tuned to suppress the third harmonic ofthe corresponding generator while passing the second, fourth and otherharmonics whereby beat effects with second and fourth harmonics of othergenerators are minimized.

9. The musical instrument as set forth in claim 8` t0- gether with asecond set of suppression circuits for the generators, each of saidsuppression circuits of the second set being individually xed by andnarrowly tuned to suppress the sixth harmonic of the correspondinggenerator while passing the ifth, seventh and other harmonics wherebybeat etects with octave harmonics of other generators are minimized.

References Cited UNITED STATES PATENTS HERMAN KARL SAALBACH, PrimaryExaminer F. P. BUTLER, Assistant Examiner U.S. Cl. X.R. S11- 1.12

